17 - 1 Flashcards
sleep architecture
Sleep is divided into distinct stages characterized by different patterns of electrical brain activity. The way these patterns come together is called sleep architecture, and it changes over the course of the life span.
Sleep cycles are 90 minutes
Stage 1 - NREM
You start in Non-Rem stage, which is the lightest
Stage 2 - NREM
a little deeper & harder to wake up
Stage 3 - NREM
deepest stage of sleep.
If someone wakes you up in Stage 3 - you are likely to be confused, groggy, not going to understand what is going on, and will be harder to wake up
REM sleep
Rapid Eye Movement - where a lot of dreaming happens.
You are close to wake, but your muscles are inhibited so that you can’t move.
circadian rhythm
We get tired because of melatonin production at the end of the day, and we wake up when melatonin is decreased.
Sunlight, through our eyes is the biggest factor. Sunlight create the response to decrease melatonin production
Homeostatic drive
based on how much sleep you have gotten recently.
If you haven’t got much sleep recently, it increases your Homeostatic drive, which then increases the adenosine.
If you haven’t slept for a long time, you will start producing more adenosine, and it will make you feel drowsy, and you will start falling sleep.
negative impacts of a lack of sleep
- Cardiovascular disease
- diabetes
- depression
- mood disorders
- physical performance
- dementia
weight management
1. Ghrelin - affects appetite - you feel hungrie
2. Leptin - you feel full
if lack of sleep - Ghrelin goes up and leptin goes down
Sleep disorders
- narcolepsy - daytime sleepiness - falling asleep at random points in the day
- Sleep apnea - snoring and stop breathing
- Chronic insomnia - difficulty falling and staying sleep
- Restless Leg Syndrome - twitching leg, need to get up and walk around - they can’t fall asleep
Sleep & Aging
As you get older, you get less quality and less duration of sleep
- Stage 3 becomes lower and lower - it is the first you lose as you age and it is the most restorative stage of sleep
NREM sleep
First three stages are grouped – non-rapid eye movement
Improves neural connections, facilitates cell restoration and repair
Stage I
Short transitional phase from wakefulness to sleep
Easily disturbed by outside stimuli
May not know they have fallen asleep
Stage II
Deeper than stage 1 but still a light sleep
Heart rate slows and body temperature drops
Bursts of brain activity
Stimuli from the environment can no longer reach higher level brain centres
Stage III
Deepest sleep stage and most necessary for feeling well rested
Supports most restorative functions
Length of stage increases after physical activity or extended periods of no sleep
Difficult to wake up quickly – may be confused
Memory and learning can become active during stages II and III
REM Sleep
Final stage of sleep
Named for the period in which the eyes move rapidly under the lids
When most dreaming occurs
Some regions of the brain are more active
Blood pressure, respiration and heart rate rise – skeletal muscles are inhibited from contracting
Sleep Cycles
First cycle through the three stages of NREM sleep
Followed by a period of REM sleep (always a final stage)
Sequence lasts about 90 min – may go through four or five cycles
Slow-wave sleep are longer in the first part of the night
More REM in the latter part of the night (dreaming)
Circadian Rhythm Variation
Genetics determines a night owl or morning lark
Morning people do better in the day but tire earlier – more sensitive to sleep loss
Evening people perform better in the evening and handle sleep loss better
Encounter external stimuli – zeitgebers – can influence our master clock
These can be activity, exercise, eating and the most important is light
Circadian Rhythm
Sleep wake pattern coordinated by the suprachiasmatic nucleus (SCN)
Every cell has a sleep wake pattern dictated by DNA – SCN coordinates them all
Night is the circadian rest phase
Insufficient sleep disrupts the repair and regeneration tasks
Circadian Rhythm affected by Light
Direct connection to the SCN via the eye
Exposed to light in the morning at a certain time regularly, causes the SCN to set the internal clock to wake up at the same time
Develop sleep habits naturally regulated
Can also reinforce unhealthy behaviour – light late at night the SCN will reset – delay sleep phase
SCN can also cause the pineal gland to secrete melatonin at dusk – preparation for sleep
Blind persons often have a difficult time with sleep due to the lack of light stimulation
We are exposed to unnatural sources of light undermining the reliance on the sun’s 24 hr cycle
Blue light produced by electronics is most disruptive and can affect sleep
Circadian rhythm disruptions
Jet lag – internal clock is set to a new environment
Experience falling asleep and waking at appropriate times
Can cause nausea and loss of appetite
Delayed sleep phase – person stays up until 4 am and sleeps until noon – if having to wake up earlier – the switch may be difficult – dysfunctional
Homeostatic sleep drive
Pressure to sleep in relation to the amount of sleep you have had in relation to wakefulness
Circadian rhythm works in opposition to the homeostatic drive
Thought to be mediated by the neurochemical adenosine
More time spent awake – more adenosine –promotes sleepiness
Sleep clears this from the brain
Caffeine Blocks Adenosine in the Brain and Delays Homeostatic Sleep Drive
How the two systems work together
Interact in a complex process of mutual opposition
Pressure to sleep is driven by the homeostatic sleep drive and directly related to how much sleep you have gotten and how long you have been awake
The circadian rhythms are not influenced by time asleep or awake – occur at the same time each day
Work independently from one another – promotes sleep and wakefulness
